Question

An electron and a proton enter a magnetic field perpendicularly. Both have same kinetic energy. Which of the following is true?

• A. Trajectory of electron is less curved
• B. Trajectory of proton is less curved
• C. Both trajectories are equally curved
• D. Both move on straight line path

Answer 1

The correct option is B Trajectory of proton is less curved

By using $r=\frac{\sqrt{2mK}}{qB}$; For both particles $q\to$ same, $B\to$ same, $K\to$ same
Hence $r\propto \sqrt{m}\Rightarrow \frac{r_e}{r_p}=\sqrt{\frac{m_e}{m_p}}$ $\because m_p>m_e$ so $r_p>r_e$
Since radius of the path of proton is more, hence its trajectory is less curved.